Why do you think the strongest of the strong bacteria are found in hospitals? Because they do a lot of cleaning and disinfecting. The weak are purged, the few who remain don't have to compete with the weak on other axes, thus they can concentrate on developing resistance.
In your home, where you don't clean as strongly and as frequently, there is a wide variety of bacteria who compete against each other, and can't spend too much on developing resistance.
Why do you think the strongest of the strong bacteria are found in hospitals? Because they do a lot of cleaning and disinfecting. The weak are purged, the few who remain don't have to compete with the weak on other axes, thus they can concentrate on developing resistance.
In your home, where you don't clean as strongly and as frequently, there is a wide variety of bacteria who compete against each other, and can't spend too much on developing resistance.